Direct air capture (DAC) of CO₂ is a critical emerging technology required to achieve ambitious net-zero emissions. Aqueous amino acid absorbents are ideal candidates for DAC and this work describes the investigation of the CO₂ absorption performance of sodium salts of β- and α-alaninate under relevant conditions for DAC by utilising synthetic CO₂ gas streams at concentrations levels found in the atmosphere (200–600 ppm). The effects of solution concentration, temperature, gas flowrate, liquid flowrate, and dissolved CO₂ concentration (i.e., CO₂ loading) on CO₂ mass transfer coefficients were investigated. The overall mass transfer coefficient was found to be independent of the gas and liquid flowrates, with larger values determined for β-alaninate solutions (0.75–1.16 mmol m⁻² s⁻¹ kPa⁻¹) than that of α-alaninate (0.65–0.87 mmol m⁻² s⁻¹ kPa⁻¹), under similar experimental conditions. The results showed that the overall mass transfer coefficient increases with increasing temperature, conversely decreasing steadily with increasing CO₂ loading. The maximum CO₂ loading capacity of the 5.0 M solutions was ∼10 % higher for β-alanine (0.651 mol CO₂/mol alaninate) than α-alanine (0.607 mol CO₂/mol alaninate) at 25.0 °C. Precipitation was found to play an important role in the CO₂ absorption processes here. Interestingly, beyond CO₂ loadings >0.12 mol CO₂/mol α-alaninate, the 5.0 M solution of α-alaninate begins to develop precipitate(s) while precipitation in the β-alaninate solution is only initiated at much higher CO₂ loadings >0.52 mol CO₂/mol β-alaninate. This study provides valuable insights into the suitability of β-alanine and α-alanine for CO₂ capture directly from the ambient air.